The general aim of this project has been to study excitable membrane characteristics by a variety of physical methods. One aspect has been to improve electrical measurements of excitable membrane characteristics consistent with physical and chemical methods for the study of nerve membrane ionic channels. Two major approaches are used. The first involves the development of methods for analysis of ionic channel admittances and/or conductances by means of oscillating potential voltage clamp techniques. Programs for carrying out this analysis are developed. The second approach involves analysis of excitable membrane characteristics by means of frequency analysis of sinusiodally modulated action potential trains locked to a larger amplitude, higher frequency sinusoidal stimulus. Improvement of bridge impedance tehcniques to achieve greater accuracy are made. Admittance measurements on giant axons and an investigation of effects of polarizations for comparison with ion conduction models are carried out. This project is supportive of a number of other projects in terms of the development of relevant hardware and software.